Unit - 6.1 Heat Transfer — PHYSICS STD 8 — Question

Boiling Point is the temperature at which liquid starts to boil. It is the temperature at which the vapor pressure of liquids becomes equal to its atmospheric pressure.
Evaporation is the process in which water evaporates from the liquid surface and changes into a gaseous state by the action of heat. It plays a very important role water cycle.
State difference between boiling and evaporation:

Boiling	Evaporation
1. During boiling, a liquid change into a gaseous state at a constant temperature, called its boiling point.	During evaporation, a liquid changes into a gaseous state at any temperature below its boiling point.
2. This process needs an external source of heat energy.	This phenomenon does not need any external source of heat energy.
3. It is a bulk process in which the gaseous state is formed from all parts of the liquid followed by the agitation of the liquid.	It is not a bulk process in which the gaseous state is formed from only the exposed surface of the liquid.
4. The boiling does not cause cooling.	The evaporation causes cooling.